A review of adenoid cystic carcinoma of the breast with emphasis on its molecular and genetic characteristics

Solid basal adenoid cystic carcinoma of the breast: A case report and literature review

RATIONALE

Adenoid cystic carcinoma (AdCC) is a rare malignancy of the breast with a low Ki-67 index and good prognosis. Owing to the rarity of breast AdCC, the misdiagnosis rate is as high as 50%, and there is no consensus or recognized guidelines for the treatment of this disease. Therefore, it is necessary to conduct a detailed clinical and pathological analysis in combination with a literature review to improve our understanding, diagnosis, and treatment of the disease.

METHODS

A 68-year-old woman sought medical attention due to a recently increasing mass in the breast. The left breast mass was 1.3 cm × 1 cm in size. We analyzed the morphology, immunohistochemistry, and molecular characteristics of the tumor removed by surgery, and reviewed relevant literature.

DIAGNOSES

Solid basal AdCC of the breast.

INTERVENTIONS

We performed biopsy, immunohistochemistry and molecular testing on surgical resection specimens.

OUTCOMES

Combining morphological and immunohistochemical features, it is consistent with solid basal AdCC of the breast, and Fish detected MYB gene break.

LESSONS

Due to the high misdiagnosis rate of AdCC, accurate histopathological diagnosis is particularly important. At present, breast conserving surgery and local tumor resection are mainly used for the treatment of breast AdCC, and postoperative adjuvant radiotherapy is feasible.

A novel EWSR1-MYB fusion in an aggressive advanced breast adenoid cystic carcinoma with mixed classical and solid-basaloid components

Breast adenoid cystic carcinoma (AdCC) with a solid-basaloid component is rare. The solid-basaloid component is usually characterized by solid nests composed of basal-like cells with marked nuclear atypia, high mitotic activity, and necrosis. Given the rarity of such tumors, information on their clinicopathological and genomic characteristics is limited. Herein, we report a case of advanced breast cancer with a poor prognosis with histological and immunohistochemical characteristics of AdCC with a solid-basaloid component. For the solid-basaloid component, fluorescence in situ hybridization (FISH) analysis revealed rearrangement of the EWSR1 and MYB genes, and immunohistochemical staining indicated MYB positivity. Next-generation sequencing-based technology revealed a novel EWSR1-MYB fusion. To our knowledge, this is the first report of an EWSR1-MYB fusion in AdCC with a solid-basaloid component and a poor prognosis. Our findings may extend the genetic understanding of AdCC and aid in the clinical diagnosis of AdCC.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

Breast lesions with myoepithelial phenotype

Myoepithelial cells (MECs) constitute a continuous layer of cells surrounding the breast glands, localised between the epithelial cells (ECs) and the basal membrane. MECs play important roles in normal mammary gland as they produce basal membrane and stimulate secretion. During neoplastic transformation, MECs act as a barrier preventing stromal invasion. MECs themselves can undergo a great variety of changes, ranging from hyperplastic to metaplastic, to neoplastic, and giving rise to a wide spectrum of morphological pictures sometimes difficult to interpret on routine diagnoses. Several benign and malignant breast tumours can present features of MECs differentiation. As these latter tumours are quite infrequent, the purpose of the present study is to offer a review of the morphological spectrum of MECs lesions, with correlations to prognosis.

Evaluation of Adjuvant Treatments for Adenoid Cystic Carcinoma of the Breast: A Population-Based, Propensity Score Matched Cohort Study from the SEER Database

Adenoid cystic carcinoma (ACC) is an extremely rare type of breast cancer. The role of adjuvant treatments for ACC remains controversial. Patients with a histology-confirmed diagnosis of ACC of the breast were identified based on the SEER (Surveillance, Epidemiology and End Results) database. Propensity score matching (PSM) was performed to balance the baseline characteristics. The Kaplan–Meier method and Cox regression models were performed to determine the impact of the adjuvant chemotherapy (CT) and radiotherapy (RT) associated with breast cancer-specific survival (BCSS) and overall survival (OS). A total of 1036 patients with ACC of the breast were included. After a median follow-up of 11.3 years, the 10-year OS and BCSS rate was 76.2% and 92.6%, respectively. After PSM, adjuvant CT converted into neither OS (Log-rank p = 1.000) nor BCSS (Log-rank p = 0.900) benefits in patients with ACC of the breast. Adjuvant RT also did not improve OS (Log-rank p = 0.060) and BCSS (Log-rank p = 0.400). According to the univariate stratified analysis, adjuvant RT was favorable for OS in patients who underwent breast-conserving surgery (HR 0.66, 95% CI 0.45, 0.99, p = 0.042). From the multivariate analysis, histology grade and nodal status were independent prognostic factors for both OS and BCSS. In conclusion, ACC of the breast presented a favorable prognosis. Adjuvant treatment, especially adjuvant CT, might not be essential for patients with this disease.

Fusion-Associated Carcinomas of the Breast: Diagnostic, Prognostic, and Therapeutic Significance

Recurrent gene fusions comprise a class of viable genetic targets in solid tumors that have culminated several recent break-through cancer therapies. Their role in breast cancer, however, remains largely underappreciated due to the complexity of genomic rearrangements in breast malignancy. Just recently, we and others have identified several recurrent gene fusions in breast cancer with important clinical and biological implications. Examples of the most significant recurrent gene fusions to date include 1) ESR1-CCDC170 gene fusions in luminal B and endocrine resistant breast cancer that exert oncogenic function via modulating the HER2/HER3/SRC complex, 2) ESR1 exon 6 fusions in metastatic disease that drive estrogen-independent ER transcriptional activity, 3) BCL2L14-ETV6 fusions in a more aggressive form of the triple negative subtype that prime epithelial-mesenchymal transition and endow paclitaxel resistance, 4) the ETV6-NTRK3 fusion in secretory breast carcinoma that constitutively activates NTRK3 kinase, 5) the oncogenic MYB-NFIB fusion as a genetic driver underpinning adenoid cystic carcinomas of the breast that activates MYB pathway, and 6) the NOTCH/MAST kinase gene fusions that activate NOTCH and MAST signaling. Importantly, these fusions are enriched in more aggressive and lethal breast cancer presentations and appear to confer therapeutic resistance. Thus, these gene fusions could be utilized as genetic biomarkers to identify patients that require more intensive treatment and surveillance. In addition, kinase fusions are currently being evaluated in breast cancer clinical trials and on-going mechanistic investigation is exposing therapeutic vulnerabilities in patients with fusion positive disease. This article is protected by copyright. All rights reserved.

Management of Adenoid Cystic Carcinoma of the Breast: A Single-Institution Study

Objective

The purpose of our study was to analyze the clinicopathologic features and surgical and oncological outcomes of adenoid cystic carcinoma (ACC) of the breast and to provide the basis for a clinical therapeutic schedule.

Methods

A total of 14 patients with primary breast adenoid cystic carcinoma treated at Cancer Hospital of the Chinese Academy of Medical Sciences from January 2000 to December 2017 were included. Data on clinical presentation, treatment strategy, and outcome, as well as the pathological features of ACC, were reviewed and analyzed.

Results

Fourteen patients were diagnosed with ACC of the breast, out of 23205 total patients treated for breast cancer (0.06%). All but three patients were postmenopausal, with a median age at diagnosis of 60.5 years (range, 39–73 years). The most common clinical presentation was a palpable mass (85.7%), and the imaging characteristics of all patients on color Doppler ultrasound and mammography were nonspecific. Six patients (42.9%) were suspected of having ACC by fine-needle aspiration cytology (FNAC) and were confirmed by postoperative histology and immunohistochemistry. All 14 patients underwent surgery, and no patient had a positive lymph node status. Median tumor size was 1.75 cm (range, 1–3 cm). Eight/14 (57.1%) patients were hormone receptor negative (HR−) and HER-2/neu (−) (HER2−). The remaining patients were hormone receptor positive (HR+). There was no significant difference in clinicopathological characteristics between the HR+ group and the HR- group (P>0.05). The mean follow-up period was 57 months. Local recurrence occurred in 14.3% of patients, 1.7% of patients had distant metastasis, all patients with local recurrence or distant metastasis were in the HR (-) group, and all patients were alive at the last follow-up.

Conclusion

ACC of the breast cannot be simply summarized as triple-negative breast cancer because it also includes a small number of hormone receptor-positive breast cancers. Establishing a preoperative diagnosis is difficult on the basis of clinical imaging examination, FNAC may be useful tool in the diagnosis. the final diagnosis can only be assessed based on the results of the histopathological and immunohistochemical examination. Breast-conserving surgery may be an alternative treatment strategy, and axillary lymph node dissection or sentinel node biopsy may not be necessary in some cases.

Special subtypes with favorable prognosis in breast cancer: A registry-based cohort study and network meta-analysis

BACKGROUND

We aimed to explore whether cribriform and adenoid cystic carcinoma had comparable prognoses to mucinous, tubular and papillary carcinoma, which were long recognized as favorable histologies by NCCN guidelines.

METHODS

A retrospective analysis based on the Surveillance, Epidemiology, and End Results Study (SEER) database (1994-2014) was conducted. The prognostic significance of all clinicopathological factors was calculated using univariate and multivariate analyses. A systematic review based on PubMed and network meta-analysis was conducted.

RESULTS

From the SEER database, the histologic subtypes of breast cancer (tubular, cribriform, adenoid cystic, mucinous, and papillary) were sorted by overall survival (OS) (94.4%, 91.6%, 90.8%, 87.6%, and 84.2%, respectively) and tubular, cribriform, mucinous, papillary, and adenoid cystic carcinoma by breast cancer-specific survival (BCSS) (99.4%, 98.4%, 97.7%, 95.2%, and 94.9%, respectively). A network meta-analysis combining 11 studies (886,649 patients) was conducted, which demonstrated consistent outcomes. SEER-based analyses revealed that, among the favorable subtypes, systemic chemotherapy did not improve OS or BCSS in hormone receptor-positive, node-negative patients, validating that these subtypes are generally associated with excellent outcomes, for which systemic chemotherapy may not be warranted.

CONCLUSIONS

Our data are consistent with guidelines suggesting that the mucinous, tubular, and papillary subtypes of breast cancer have favorable histologies. SEER data and meta-analysis supports this favorable category to include adenoid cystic and cribriform carcinoma, whose OS and BCSS outcomes are comparable to the former three. These findings add to the body of data, suggesting that patients with these histologic subtypes confer excellent prognosis, which may guide optimal therapeutic management strategies.

Rare epithelial breast cancer: surgery and adjuvant therapy

Breast cancer is a heterogenous disease, exhibiting a wide range of morphological phenotypes shaping its prognosis and clinical course. However, optimal management of rarer breast cancer subtypes is often undefined and controversial in literature due to the lack of large studies and randomised trials. This review aims to discuss the treatment of 13 rare epithelial subtypes, focussing on surgery and adjuvant therapies.

A case of adenoid cystic carcinoma of the breast

An 85-year old woman who had a large tumor in the left breast came to our out-patient clinic. Computed tomography showed multiple lung tumors in addition to a huge tumor in the left breast. A needle biopsy brought about a histological diagnosis of ductal carcinoma. A simple mastectomy was performed and a histological examination using the resected specimen demonstrated a coexistence of an adenoid structure and a false ductal structure according the histologic characteristics of adenoid cystic carcinoma, which is quite rare among breast tumors. J. Med. Invest. 65:289-291, August, 2018.

Primary Adenoid Cystic Carcinoma of the Liver: Case Report and Review of the Literature

Adenoid cystic carcinoma (ACC) is an uncommon tumor primarily occurring in the salivary glands and is relatively rare in other sites. In the liver, only one primary adenoid cystic carcinoma has been reported in the English literature. Here we presented a primary hepatic adenoid cystic carcinoma in a 44 years old male. We described its histopathologic features and its immunohistochemical profile, and reviewed the literature. The surgical treatment and patient follow up information was also presented.

Adenoid cystic carcinoma of the breast: Experience at a tertiary care centre of Northern India

INTRODUCTION

Adenoid cystic carcinoma of the breast (breast-ACC) is a rare tumor with a favorable prognosis, despite its triple-negative status and special type of basal-like tumor for which scant population-based descriptive data exist. We sought to provide new population-based information on breast-ACC in India. Due to the paucity of the number of cases, the natural history of the disease is not fully understood. This study was undertaken to examine the clinico-pathological characteristics of the disease and to evaluate the outcome of surgical intervention in a tertiary referral care centre.

MATERIALS AND METHODS

A retrospective analysis of all patients diagnosed and treated for ACC Breast in our hospital over the past 10 years was carried out (2005-2015). A database of the characteristics of these patients was developed. In all, 14 patients were identified. The investigations performed included routine blood investigations, chest X-ray, bone scan and either an ultrasound or a CT scan.

RESULTS

During the time period of 10 years, of 2347 with breast malignancy admitted to our department, only 14 were diagnosed as having ACC (3.15%). All patients were women (100%). The patients had a median age of 60.7 years (range 37-81). The most common symptom was lump in the breast. Two patients (14.2%) presented with nipple and skin retraction and two patients (14.2%) were asymptomatic with the diagnosis made by an incidental finding on routine examination. The CT and/or magnetic resonance imaging (MRI) showed the typical features of carcinoma breast. All the 14 patients were taken up for surgery. Nine patients underwent Modified radical mastectomy and five patients underwent Breast conservation surgery. Axillary lymph node dissection was carried out in seven patients and sentinel lymph node biopsy in the remaining. Tumor cells had a characteristic histologic pattern of ACC of the breast. Perineural invasion was present in six cases.

DISCUSSION

ACC of the breast is a very rare malignancy, accounting for less than 0.1% of all breast neoplasms. It affects the left and right breasts equally and tumors arise irrespective of the breast quadrants. However, in about 50 percent of patients, lesions are found in subareolar region. Pain or tenderness described in the minority of cases has not been correlated with histologically-confirmed perineural invasion. ACC is categorized as a basal-like subtype of breast carcinoma. Most cases are macroscopically well-circumscribed. Occasionally, pink, tan, or gray microcysts are evident. A tumor typically consists of a dual-cell population of luminal and myoepithelial-basal cells which may be arranged in one or more of three architectural patterns: tubular-trabecular, cribriform, and solid-basaloid. There is no consensus on the optimal management for patients with ACC of the breast. Based on its indolent clinical course and favorable outcome, ACC of the breast is generally cured by breast-conserving surgery, such as wide excision or quadrantectomy with or without radiotherapy.

CONCLUSION

Breast-ACC among women is characterized by ER-negative/PR-negative expression, rare regional lymph node involvement, a favorable prognosis with excellent survival, and absence of associated cancers. These findings reinforce the importance of tailored treatments for breast-ACC and the apparent heterogeneity of basal-like breast cancers.

Adenoid cystic carcinoma of the breast, 20 years of experience in a single center with review of literature

BACKGROUND

Adenoid cystic carcinoma (ACC) of the breast is a rare type of breast cancer, which presents inconsistencies in the optimal management strategy.

METHODS

A retrospective review of prospectively collected data, spanning the last 20 years, was performed using the cancer registry database at our institution.

RESULTS

Six patients were diagnosed with ACC of the breast, out of 5,813 total patients diagnosed with breast cancer (0.1%). Our identified patients had a median age of 66, all with the early stage cancer (Stage I/II). The average size of the breast lesion was 1.62 cm, and nodal status was negative for all cases. All patients had resection as primary therapy (partial or total mastectomy), with one patient also undergoing external beam radiation and tamoxifen hormonal therapy. Median follow-up was 85 months, with all patients being disease-free at last follow-up.

CONCLUSIONS

ACC of the breast has an indolent course, despite triple negative status. Our study suggests that radiation may not be warranted and confirms the rarity of axillary node metastases, indicating that sentinel node excision may also not be necessary. Ultimately, the hope is that our findings along with the reviewed literature will aid in determining the most appropriate options for management of ACC of the breast.

Breast adenoid cystic carcinoma: report of a case with emphasis on routine sonographic findings and shear wave elastography

Adenoid cystic carcinoma (ACC) of the breast is a rare malignant tumor. Its sonographic characteristics have been described in some reports, but there are few such reports available that describe the sonoelastographic findings of this tumor and provide additional information about the nature of the lesion. In this case report, we describe the routine sonographic findings and shear wave elastography findings of a breast adenoid cystic carcinoma in a 53-year-old woman.

36 cases adenoid cystic carcinoma of the breast in China: Comparison with matched grade one invasive ductal carcinoma-not otherwise specified

OBJECTIVE

The aim of this study was to investigate the clinicopathological characteristic of adenoid cystic carcinoma (ACC).

MATERIALS AND METHODS

The clininopathological features, along with relapse free survival(RFS) and overall survival(OS) of 36 patients with ACC were retrospectively investigated and compared with those of 108 grade 1 invasive ductal carcinoma not-otherwise-specified (G1-IDC-NOS) patients.

RESULTS

Most cases of ACC were ER, PR and HER-2 negative which was classified as triple-negative subtype. Five cases were concomitant with other pathological types of cancer. Axillary lymph node dissection(ALND) was performed in 31 patients and 2 of them with lymph nodes metastasis. Two patients died of lung metastases at 46 and 116 months after the surgery respectively. Compared with G1-IDC-NOS, ACC showed lower Ki-67 index, less lymph nodes metastasis, lower P53 expression, and higher proportion in location of upper outer quadrant of breast. There was no difference of OS and RFS between ACC and G1-IDC-NOS.

CONCLUSIONS

ACC of the breast was a rare disease with a good prognosis although most of them were classified as triple-negative subtype. And the value of axillary node dissection and adjuvant therapy needs to be further investigated.

Adjuvant radiation therapy and survival for adenoid cystic carcinoma of the breast

PURPOSE

The assess the clinical value of different types of surgical procedures and further analyze the effect of adjuvant radiation therapy (RT) for adenoid cystic carcinoma (ACC) of the breast.

METHODS

Patients with ACC of the breast were identified using a population-based national registration database (Surveillance, Epidemiology, and End Results, SEER). The Kaplan-Meier method and Cox regression models were performed to determine the impact of the surgical procedures and adjuvant RT associated with cause-specific survival (CSS) and overall survival (OS).

RESULTS

A total of 478 patients with ACC of the breast were identified. The median follow-up was 59 months. The 10-year CSS and OS were 87.5% and 75.3%, respectively. For the Kaplan-Meier analysis, the 5-year CSS were 96.1%, 91.8%, 90.2%, and 94.1% in patients that received lumpectomy + adjuvant RT, lumpectomy alone, mastectomy alone, and mastectomy + adjuvant RT, respectively (p = 0.026). In the multivariate Cox analyses, lumpectomy + adjuvant RT was an independent prognostic factor for CSS and OS. Patients that received lumpectomy + adjuvant RT had better survival rates than patients that underwent lumpectomy only (CSS, p = 0.018; OS, p = 0.031) and mastectomy only (CSS, p = 0.010; OS, p = 0.004).

CONCLUSION

ACC of the breast has an excellent prognosis. Breast-conserving surgery is a reasonable alternative for patients with ACC of the breast, and adjuvant RT after lumpectomy improved survival rates.

Axillary lymph node metastases in adenoid cystic carcinoma of the breast. A rare finding

Adenoid cystic carcinoma (ACC) of the breast is a rare malignant salivary-type neoplasm that has a good prognosis and represents less than 1% of all breast cancers. It is a triple negative carcinoma that presents as a painful mass. The mean age at the time of diagnosis is 50-60 years old. The solid variant of this type of tumour with basaloid features and presence of nodal metastases is very rare and considered to have a more aggressive clinical course. We present a case with presence of axillary lymph node metastases that was successfully treated with no evidence of recurrence one year after the diagnosis and review the literature.

The unique luminal staining pattern of cytokeratin 5/6 in adenoid cystic carcinoma of the breast may aid in differentiating it from its mimickers

Adenoid cystic carcinoma (AdCC) of the breast is an uncommon but distinct neoplasm composed of a dual cell population polarized around true glandular (luminal) spaces and pseudolumina. The aim of this study was to clarify whether various immunohistochemical markers (CK7, EMA, CD117, p63, calponin, CD10, S100, CK5/6, CK14, vimentin, and type IV collagen) can distinguish between the two cell types in classical AdCC (n = 14) and in collagenous spherulosis (n = 5). The sensitivity and specificity of these 11 markers to distinguish luminal from abluminal cells were evaluated using a curve created by plotting the true-positive rate (sensitivity) against the false-positive rate (1 - specificity) at threshold settings of 0, 10, 50, and 70 %. The most sensitive and specific markers for luminal cells in AdCC were CK7 and EMA; those for abluminal cells were type IV collagen, p63, and vimentin. CD10 and S100 did not act as abluminal markers in AdCC. CK5/6, one of the basal/myoepithelial markers, was expressed more frequently in luminal than in abluminal cells of AdCC. Thus, CK5/6 immunostaining resulted in a reverse expression pattern, analogous to what we recently documented in clear cells in mammary adenomyoepithelioma. In conclusion, compared with myoepithelial/abluminal cells of normal breast or collagenous spherulosis, the neoplastic abluminal cells of classical AdCC are characterized by enhanced vimentin and attenuated CD10 and S100. Furthermore, the luminal cells of AdCC show a unique aberrant staining pattern for CK5/6 that may aid in the differential diagnosis.

Diagnosis of adenoid cystic carcinoma of the breast using fine-needle aspiration cytology: A case report and review of the literature

Adenoid cystic carcinoma (ACC) of the breast is a rare variant of breast malignancy and is associated with an excellent prognosis. ACC accounts for 0.1% of all breast carcinomas. It has favorable biological characteristics and an excellent prognosis. A 77-year-old woman presented with a lump in the right breast. Ultrasonography and mammography showed a 12-mm, well-defined, lobulated mass in the retroareolar region of the right breast. The lump was diagnosed as ACC on the basis of immunohistochemical staining results for c-kit (CD117), muscle-specific actin, p63, estrogen receptor, and progesterone receptor using a fine-needle aspiration cytology (FNAC) specimen. This diagnosis was subsequently confirmed by excision biopsy. To the best of our knowledge, this is the first case of ACC of the breast to date to be diagnosed on the basis of immunohistochemical staining of an FNAC cell block material. From our experience, we recommend the usage of cell block material for immunohistochemical studies to accurately diagnose ACC of the breast.

Malignant adenomyoepithelioma combined with adenoid cystic carcinoma of the breast: a case report and literature review

Background

Malignant adenomyoepithelioma and adenoid cystic carcinoma are both rare malignant epithelial-myoepithelial tumors of the breast. We report a very rare case with a malignant adenomyoepithelioma combining with adenoid cystic carcinoma in a single mass.

Case presentation

A 61-year-old female presented with a palpable painless mass in the right breast. Mammography revealed a large irregular dense shadow without obvious internal calcification. A simple lumpectomy was performed, and a 1.6cm well-circumscribed pale-tan nodule was presented. Histologically, the nodule was composed of two obscure lobules. One exhibited typical histological image of adenoid cystic carcinoma, the other one showed the image of epithelial-myoepithelial carcinoma of salivary gland, and support the diagnosis of biphasic malignant adenomyoepithelioma. Transition between the two lobules was gradual. Immunohistochemically, CK18 and P63 highlighted the epithelial and myoepithelial cells respectively in both lesions. CD117 was positive in the epithelial cells of adenoid cystic carcinoma, but was totally negative in malignant adenomyoepithelioma.

Conclusion

This report is, to our knowledge, the first case that combines these two tumors in a single mass. In addition, we present a review of the literature. The histogenesis of these tumors is also discussed.

Virtual Slides

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Rare breast cancer subtypes: histological, molecular, and clinical peculiarities

Breast cancer encompasses a collection of different diseases characterized by different biological and pathological features, clinical presentation, response to treatments, clinical behavior, and outcome. On the basis of cell morphology, growth, and architecture patterns, breast cancer can be classified in up to 21 distinct histological types. Breast cancer special types, including the classic lobular invasive carcinoma, represent 25% of all breast cancers. The histological diversity of breast carcinomas has relevant prognostic implications. Indeed, the rare breast cancer group includes subtypes with very different prognoses, ranging from the tubular carcinoma, associated with an indolent clinical course, to metaplastic cancer, whose outcome is generally unfavorable. New approaches based on gene expression profiling allow the identification of molecularly defined breast cancer classes, with distinct biological features and clinical behavior. In clinical practice, immunohistochemical classification based on the expression of human epidermal growth factor receptor 2 and Ki67 is applied as a surrogate of the intrinsic molecular subtypes. However, the identification of intrinsic molecular subtypes were almost completely limited to the study of ductal invasive breast cancer. Moreover, some good-prognosis triple-negative histotypes, on the basis of gene expression profiling, can be classified among the poor-prognosis group. Therefore, histopathological classification remains a crucial component of breast cancer diagnosis. Special histologies can be very rare, and the majority of information on outcome and treatments derives from small series and case reports. As a consequence, clear recommendations about clinical management are still lacking. In this review, we summarize current knowledge about rare breast cancer histologies.

Adenoid cystic carcinoma of the breast: A case report and literature review

Adenoid cystic carcinoma (ACC) is a rare malignant tumor of the breast that occurs in <0.1% of all patients diagnosed with breast cancer. The mean patient age at the time of diagnosis is 50–60 years. Typically, the tumor presents as a subareolar mass or as pain in the breast. While the radiological appearances of ACC are generally non-specific, the diagnosis can be made on fine-needle aspiration cytology. In the present study, a 58-year-old female patient was admitted to the Department of Radiation Oncology (Karadeniz Technical University, Faculty of Medicine, Trabzon, Turkey) with complaints of pain in the upper outer quadrant of the right breast. An excision biopsy of a lump in the upper outer quadrant revealed ACC, and perineural invasion was present. Subsequently, the patient underwent breast conservation surgery and sentinel lymph node dissection. Pathology from the second surgery depicted ACC in the form of microscopic foci around the initial surgical cavity, with two reactive sentinel lymph nodes and the closest negative margin at 2 mm. The patient was treated with radiotherapy following the surgery. No recurrence and metastasis were found after 20 months of follow-up. In conclusion, mammary ACC is a rare malignant neoplasm of the breast. Although surgery is the main treatment, the optimal adjuvant treatment of ACC of the breast has not yet been determined due to its low incidence.

Metastatic Cancer of Cowper's Gland: A Rare Cancer Managed Successfully by Molecular Profiling

Cancer of Cowper's gland is a very rare cancer. This case represents the 9th case in the medical literature. As such, there are no phase II or phase III trials to guide treatment. In this article, we report the successful treatment of a patient over a 7-year period guided solely by molecular profiling. Through multiple cycles to treatment, the cancer was controlled using drugs targeting c-kit, as the cancer steadily increased the expression of c-kit. This report also documents the use of a novel drug combination based on sunitinib that was well tolerated and may warrant testing in other c-kit-dependent cancers.

Myoepithelial and epithelial-myoepithelial, mesenchymal and fibroepithelial breast lesions: updates from the WHO Classification of Tumours of the Breast 2012

In the 4th edition of the WHO Classification of Tumours of the Breast, myoepithelial lesions are retitled myoepithelial and epithelial-myoepithelial lesions in order to better reflect the dual participation of luminal and myoepithelial compartments in some key entities. Malignant myoepithelioma, described as a section within the chapter on myoepithelial lesions in the 3rd edition, is recognised in the 4th edition as part of metaplastic carcinoma. Adenomyoepithelioma with malignancy is categorised in terms of the cellular component undergoing malignant transformation. The list of antibodies that can be used for identifying myoepithelial cells is updated. Among mesenchymal lesions, new additions are nodular fasciitis and atypical vascular lesions, while the haemangiopericytoma is removed. The 3rd edition stated that pathological prediction of behaviour of phyllodes tumours is difficult in the individual case. In the 4th edition, some progress has been made in prioritisation and weighting of histological parameters that can potentially estimate probability of recurrence. The WHO Working Group advocates leaning towards a diagnosis of fibroadenoma in cases where there is histological uncertainty in distinction from a benign phyllodes tumour, or adopting the neutral term 'benign fibroepithelial neoplasm', as the clinical behaviour of fibroadenoma overlaps with that of benign phyllodes tumour. The 3rd edition terminology of 'periductal stromal sarcoma' is revised to 'periductal stromal tumour', akin to the widespread consensus to avoid the use of the term 'cystosarcoma' in the context of phyllodes tumours.